This invention relates to an improved process for the synthesis of N-substituted arylsulfonamides. More particularly, the invention relates to the preparation of N-substituted arylsulfonamides by reacting an aliphatic amine with the crude reaction product from the reaction of an aryl hydrocarbon and chlorosulfonic acid without separation of by-products or unreacted materials from the aryl sulfonyl chloride present in the crude reaction product.
A typical method for the preparation of N-alkyl substituted arylsulfonamides as set forth in The Organic Chemistry of Sulfur involves the use of an aryl sulfonyl chloride compound, generally prepared from the reaction of chlorosulfonic acid with a suitable aryl compound such as benzene, alkyl substituted benzene compounds, naphthalene and the like. The aryl sulfonyl chloride is reacted with a primary or secondary alkyl amine including cyclic amines such as piperidine and polymethylenediamines. The reaction is usually conducted in an inert solvent such as benzene, employing two equivalents of amine for one of the sulfonyl chloride, or in the presence of aqueous alkali where only one equivalent of amine may be necessary. Where the starting ingredients are a solid, the addition of an organic solvent immiscible with water is usually desirable. Alternatively, the reaction may also be carried out in the presence of triethyl amine or pyridine.
In order to avoid contamination, maintain sufficient yields and avoid the possibility of undesirable side reactions, the aryl sulfonyl chloride is typically refined, usually by water quenching, washing in the presence of a solvent, solvent stripping, distillation, and sometimes crystallization, to remove by-products and unreacted ingredients which may be present from the preparation of the aryl sulfonyl chloride.
U.S. Pat. No. 2,757,156 to Dazzi discloses preparation of N-alkyl alkene sulfonamides by reacting a paraffin with a mixture of sulfur dioxide and chlorine followed by reacting the resulting sulfonyl chloride with a primary alkyl amine. In an example, N-heptane sulfonyl chloride is prepared and then recovered by distillation of the reaction product prior to reaction with monoethylamine.
U.S. Pat. No. 3,246,007 to Meyer et al discloses oxadiazole benzene sulfonamide compounds. In the examples, the intermediate benzene sulfonyl chloride is isolated and purified prior to reaction with the amines.
Such refined aryl sulfonyl chloride is usually considered particularly important where the N-substituted aryl sulfonamide is to be used as a polymer-modifying additive, e.g., plasticizer or crystallizer in the preparation of molded compositions.
It has now been found that N-substituted aryl sulfonamides may be prepared without the multistep and costly purification of the aryl sulfonyl chloride intermediate and still function adequately in polymer modification of molded products.